Method for making antifouling coating composition containing hydrolyzed organotin siloxane polymer

ABSTRACT

A solution containing hydrolyzed organotin siloxane polymeric material is formed by hydrolyzing an organotin R-oxy siloxane in a water miscible solvent; R being an alkyl or alkoxyalkyl group with less than six carbon atoms. A water immiscible solvent is added and the water miscible solvent and R-alcohol from hydrolysis are removed by distillation. A marine antifouling coating can be made when the water immiscible solvent evaporates from the solution. A preferred embodiment hydrolyzes tributyltin ethoxysiloxane in ethyl alcohol with xylene as the water immiscible solvent.

FIELD OF THE INVENTION

This invention relates to making a solution containing hydrolyzedorganotin siloxane polymeric material suitable for use in marineantifouling coatings.

BACKGROUND OF THE INVENTION

Compositions have been developed for protecting marine surfaces fromfouling organisms, including a linear or cross-linked polymer having asiloxane backbone and trisubstituted tin radicals such as tributyl tinbonded to silicon atoms by way of an oxygen atom. The biologicallyactive polymer can be used for forming coatings for steel, concrete, orother surfaces exposed to marine environments for inhibiting the growthof fouling organisms. In some embodiments the polymer is present as anadditive in a coating composition. In other embodiments the cross-linkedpolymer forms a portion of the binder of the coating.

U.S. Pat. No. 4,080,190 by Law and Gysegem, which is hereby incorporatedby reference, discloses such compositions with a variety of organotinradicals and synthesis techniques. The ratio of tin to silicon atoms inthe polymer can be varied for obtaining different properties in thepolymer. When the proportion of tin is low, a cross-linked polymer canbe formed by hydrolysis and polycondensation of a siloxane-tinprecursor. In an exemplary embodiment the precursor is formed byreaction of tetraethoxysilane or a short chain ethosyxiloxane with acarboxylic acid derivative containing a tin radical, such as tributyltinacetate. A prepolymer can be formed by partially or completelyhydrolyzing the precursor. Water and a hydrolysis catalyst such ashydrogen ion or hydroxyl ion are added to the solvent. Upon evaporationof the solvent polycondensation occurs, yielding the desired polymer.

It is sometimes convenient to hydrolyze the precursor to a prepolymerbefore completing a coating composition since prehydrolysis can reducethe curing time of a coating. Polycondensation of the prepolymer hasheretofore been inhibited by retaining the prepolymer in ethyl alcoholor similar solvent. Ethyl alcohol is a product of hydrolysis of theprecursor when, for example, an ethoxysilicate is employed in thesynthesis. When such a coating is applied, evaporation of ethyl alcoholresults in polycondensation in the coating.

Ethyl alcohol and similar water miscible solvents may not be compatiblewith other ingredients in the coating composition. This is particularlytrue when the coating composition includes a chlorinated rubber, forexample. It is therefore desirable to provide a solution containingpolymeric material which is compatible with such coating compositions.

BRIEF SUMMARY OF THE INVENTION

Thus, in practice of this invention, a solution containing hydrolyzedorganotin siloxane polymeric material is formed by combining anorganotin R-oxy siloxane, where R represents a group consisting of alkyland alkoxyalkyl radicals containing less than six carbon atoms, a watermiscible solvent, water, a hydrolysis catalyst, and a water immisciblesolvent. After hydrolysis of the organotin R-oxy siloxane, the watermiscible solvent and R-alcohol from the hydrolysis reaction are removedby distillation. The water immiscible solvent, such as xylene, ispreferably added after hydrolysis. Surprisingly, it is found thatprecipitation of such polymeric material does not occur from the waterimmiscible solvent.

DESCRIPTION

As used herein, the term "precursor" refers to an organotin R-oxysiloxane where R represents a group consisting of alkyl and alkoxyalkylradicals containing less than six carbon atoms, the term "prepolymer"refers to a precursor that is partly or completely hydrolyzed but notcompletely condensed; the term "polymer solution" refers to a solutionof a water immiscible solvent containing a polymeric material; and theterm "polymer" refers to a thoroughly polycondensed prepolymer includinglinear and/or cross-linked polymers.

Precursors for forming prepolymers for marine antifouling compositionshave the formula ##STR1## where m is from about 1 to about 10; whereeach X is independently selected from the group consisting of R and Y;where each Y in the precursor independently is a trisubstituted tinradical having the formula ##STR2## where R₁, R₂, and R₃ areindependently selected from the group consisting of alkyl, cycloalkyl,and aryl radicals, where R₁, R₂, and R₃ contain in combination up toabout 18 carbon atoms, and where the X's are selected so that the ratioof tin atoms to silicon atoms in the precursor is in the range of fromabout 1:50 to about 1:1. The Y's in the precursor can be the same ordifferent. Depending upon the ratio of tin atoms to silicon atoms in theprecursor and the nature of the R₁, R₂, and R₃ groups on the tin, theprecursor can be a liquid or a waxy solid at room temperature.

In a mixture of precursor molecules, m represents the average number ofsilicon atoms per precursor molecule. Generally there is a randomdistribution of molecules comprising more and less than m silicon atoms.For example, where m equals 5, precursor molecules containingpredominantly 4, 5 or 6 silicon atoms are present. A few molecules withlarger and smaller numbers of silicon atoms can also be present.

In the above formula for the precursors, preferably m is less than about10 so the precursor can be polymerized by hydrolysis andpolycondensation. Preferably m is an average of about five. Such amaterial comprises a mobile liquid with a high SiO₂ content having ampleside groups for substitution of tin radicals and subsequent hydrolysisand polycondensation. A suitable material is available from UnionCarbide Chemical Company as "Ethyl Silicate 40". This is an ethylpolysilicate or ethoxysiloxane having an average of about five siliconatoms per molecule, that is, m equals five, although individualmolecules may comprise as few as one silicon atom. This material has anSiO₂ content of about 40%.

R comprises alkyl and alkoxyalkyl radicals containing less than about 6carbon atoms so that the alcohol analog of R formed during hydrolysis ofthe precursor has sufficient volatility for distillation. Generally, thehigher the molecular weight of R, the lower the volatility of itsalcohol analog. Exemplary of the radicals which R can be are methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, methyloxymethyl,methyloxyethyl, and the like. Preferably X is the ethyl radical sincetransesterification yields ethyl acetate in a preferred embodiment andhydrolysis yields ethyl alcohol, each of which is readily removed bydistillation.

R₁, R₂, and R₃ can be lower alkyl radicals containing less than about 10carbon atoms such as methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, amyl, hexyl, octyl, nonyl, isooctyl radicals, andthe like. These can also be a substituted lower alkyl radical.Substituents include chloride, bromide, ether and aryl substituents, andthe like.

R₁, R₂, and R₃ can be a lower cycloalkyl radical such as the cyclohexylradical and substituted lower cycloalkyl radicals.

R₁, R₂, and R₃ can be an aryl radical such as the phenyl radical andsubstituted phenyl radicals. Substituents include chloride, bromide,ether, and alkyl substituents, and the like. Thus R₁, R₂, and R₃ can bechlorophenyl, bromophenyl, nitrophenyl, tolyl, xylyl, ethylphenyl, andthe like. When R₁, R₂, and R₃ are all aryl radicals and the precursorhas a tin to silicon atom ratio of about 1:5, the prepolymer is a solidwith only slight solubility in common solvents. Thus, if the prepolymeris to be used for forming a binder for coating compositions, R₁, R₂, andR₃ generally cannot all be aryl radicals.

Preferably, R₁, R₂, and R₃ are the same because trisubstituted tincompounds where the tin is substituted with the same radical arecommercially available. However, R₁, R₂, and R₃ can be different such aswhere Y is the octyl-dimethyl tin radical.

The total number of carbon atoms comprising a trisubstituted tin moietyhas a large effect on its biological activity. The effect appears to beone of size rather than chemical or electronic effect. For example, theoctyldimethyl and the tributyl tin radicals, which have about the samenumber of carbon atoms, exhibit about the same toxicity toward mammalsand fouling organisms. In general, small moieties, such as the trimethyltin and triethyl tin radicals, show only slight toxicity toward bacteriaand marine fouling organisms, but extremely high toxicity towardmammals, including man. Tripropyl tin and tributyl tin, on the otherhand, exhibit low toxicity toward man, but are the most effectivetrialkyl tin compounds for antifouling use. As the total number ofcarbons in a trialkyl tin compound increases above about 12 to 14, boththe human toxicity and antifouling activity decrease due to the increaseof the total number of carbon atoms.

Preferably, when R₁, R₂, and R₃ are alkyl radicals, the total number ofcarbon atoms in R₁, R₂, and R₃ in combination is less than about 14carbon atoms for high biological activity. Generally, R₁, R₂, and R₃contain less than about 18 carbon atoms in combination so thatcompositions effective in protecting materials from growth of marineorganisms can be prepared.

Preferably, R₁, R₂, and R₃ are selected so that Y is the tributyl,tripropyl, triphenyl or tricyclohexyl tin radical. These radicals arepreferred because they are broad-spectrum toxicants, expecially for manymarine organisms, and display minimal toxicity to man. The tributyl tinradical is particularly preferred.

A precursor preferably has a ratio of tin to silicon atoms greater thanabout 1:50 because at ratios less than about 1:50 a coating preparedwith the prepolymer shows inadequate biological activity to be of muchcommercial value. The maximum ratio of tin to silicon atoms in theprecursor is preferably about 1:1. If the ratio is higher than about 1:1steric hindrance by the tin moiety may inhibit extensivepolycondensation and significantly limit the molecular weight of theresultant polymer.

The optimum tin to silicon atom ratio of a prepolymer used for forming abinder is a balance of competing considerations. On one hand, the higherthe tin to silicon atom ratio, the more effective and more long-lived isa coating including the prepolymer. However, at higher ratios of tin tosilicon atoms, curing of the prepolymer by hydrolysis andpolycondensation to form a polysiloxane becomes progressively moredifficult. At tin to silicon atom ratios greater than about 2:5, theprepolymer is not suitable for preparing binders for coatingcompositions because the polymer remains soft and does not cure tosufficient hardness to be used as a coating. It is believed that aprepolymer having a tin to silicon atom ratio greater than about 2:5 isunsatisfactory for forming binders because the bulky organotin groupprevents polymerization by either blocking the attack of water or thereactive sites of the precursor, or by inhibiting condensation of theintermediate silanol formed during hydrolysis with another silanolgroup.

A prepolymer for forming a biologically active polysiloxane binderpreferably has a tin to silicon atom ratio of from about 1:12 to about1:3. In this range it has been found that a hard, clear,solvent-resistant film exhibiting effective and long-lived biologicalactivity in preventing fouling on marine surfaces can be formed.

The precursor is preferably prepared by reacting a silicate having theformula ##STR3## with about n moles per mole of the silicate of acarboxylic acid derivative having the formula ##STR4## where m and Y areas above, and where the ratio of n to m is in the range of from about1:50 to 1:1 to give a desired tin to silicon atom ratio as describedabove. R₄ represents the group consisting of alkyl and alkoxyalkylradicals containing less than about six carbon atoms, i.e., R₄ is theorganic portion of the group from which X is selected. Each R₄ may bethe same or different. Preferably, R₄ is the ethyl radical.

R₅ is selected from the group consisting of hydrogen, and alkyl,cycloalkyl, and alkoxyalkyl radicals. R₅ is selected for convenience,i.e., so that the carboxylic acid ester formed in the reaction issufficiently volatile to be removed easily from the product. Preferablya trisubstituted tin acetate is employed.

Exemplary of silicates and carboxylic acid derivatives which can be usedare "Ethyl Silicate 40" and tributyltin acetate. "Ethyl Silicate 40" andtributyltin acetate react according to the equation ##STR5## Thetributyltin substituted silicon atoms are randomly located along thechain, and a single silicon atom can be substituted by none, one, two orthree tributyltin groups.

The reaction of the silicate and the carboxylic acid derivative isconducted at an elevated temperature, and at least at a temperaturesufficiently high that the carboxylic acid derivative melts. Thesilicate and carboxylic acid derivative are reacted at a temperaturebelow the temperature at which the precursor prepared from the silicateand carboxylic acid derivative decomposes. Decomposition may beevidenced by darkening of the precursor and a hydrocarbon-like odor. Forexample, when preparing a precursor from tributyltin acetate and EthylSilicate 40, the temperature should be maintained from about 160° toabout 180° C.

Another method for preparing the precursor is to combine a silicate, asdescribed above, with about n/2 moles of water per mole of the silicateand n/2 moles per mole of the silicate of a bis-trisubstituted tin oxidehaving the formula Y--O--Y where Y and n have the same meaning as above.Generally, a silicate reacts at a lower temperature with a tin oxidethan with the carboxylic acid derivative of the tin oxide. For example,bis-tributyltin oxide reacts at a fast rate with Ethyl Silicate 40 inthe presence of water at about 85° C. compared to the 160° C. requiredwhen tributyltin acetate is used.

Another method for preparing the precursors is to combine a silicate asdescribed above with about n moles of a trisubstituted tin hydroxidehaving the formula Y--OH, where Y and n have the same meaning above, permole of the silicate. The silicate and tin hydroxide are combined at atemperature below the temperature at which the precursor formed from thetin hydroxide and the silicate decomposes.

The fully polymerized polysiloxane is prepared from the precursor byhydrolysis followed by polycondensation. The hydrolysis ofalkylsilicates at neutral pH is generally too slow to be able to use thesilicate as a binder in coating formulations. However, in either acidicor basic medium, the rate of hydrolysis is appreciably increased. Inacid conditions, achieved by adding small amounts of an acid to thewater used in the hydrolysis, the equilibrium conditions are reached inhours. These equilibrium conditions, which are, ##STR6## all occursimultaneously. Also under acid conditions, the tendency for linearchain extension and cyclization is much stronger than for cross-linking.All of these account for the liquid nature of the hydrolyzed prepolymerwhen in a closed system where no alcohol can escape. In the atmosphere,the alcohol can evaporate, thereby driving the equilibrium toward thecondensed silicate form.

Dilute aqueous hydrochloric acid can be used to catalyze the hydrolysisof the precursor. Other acids which can be used as catalysts includemineral acids such as sulfuric acid, orthophosphoric acid, and nitricacid, and organic acids such as trichloroacetic acid, formic acid andoxalic acid. The amounts to be used vary for each acid, but the optimumquantity can readily be determined by a chemist of ordinary skill in theart. The action of organic acids generally is slower than that ofinorganic acids.

Hydrolysis of the precursor can also be catalyzed by a hydroxyl sourcewhich itself is nonreactive with the precursor, but which reacts withmoisture to produce hydroxyl ions, such as described in U.S. Pat. No.3,653,930, issued to Law et al, and incorporated herein by reference.This patent describes catalyzing hydrolysis of silicates with a hydroxylsource nonreactive with the silicate and reactive with moisture toproduce hydroxyl ions. Exemplary of hydroxyl sources are organic aminessuch as mono-, di-, and triethanolamine, diamylamine, cyclohexylamine,piperidine, and the like, and inorganic hydroxyl sources such aspotassium, sodium, and lithium hydroxide.

A solvent may also be used when the precursor is hydrolyzed. Thus, theprecursor is dissolved in a solvent such as ethanol before hydrolysis.Exemplary of the solvents which can be used are those listed in Table Iof U.S. Pat. No. 3,653,930. Preferably, the solvent is the same alcoholas the alcohol from hydrolysis reaction. For example, when the precursorcomprises tributyltin ethoxysiloxane, ethyl alcohol results fromhydrolysis and the preferred solvent is ethyl alcohol. In practice ofthis invention, such solvent is distilled from the solution and it ispreferable to recover a single distillate for reuse in the process orfor other uses without further separations.

It has previously been considered appropriate to supply a coatingcomposition including a precursor or prepolymer in a package with ahydrolysis catalyst. For example, a precursor can be packaged with asource of hydroxyl ions so that upon addition of water, hydrolysis andpolycondensation can occur. It has not been considered appropriate tohydrolyze the precursor with hydroxyl ion catalysis an appreciable timebefore application as a coating because of the possibility of prematuregellation and short shelf life. When the precursor is hydrolyzed withacid catalysis, the precursor, a water miscible solvent, water, and acidcan be packaged together for reducing the curing time of the appliedcoating. In some embodiments, the acid catalyzed coating composition canbe provided in a single container. In the acid catalyzed product, it hadpreviously been considered necessary to prevent evaporation of thealcohol product of hydrolysis to prevent premature polycondensation andless than complete hydrolysis of the precursor is preferred.

It has been found that gellation of the organotin siloxane can beinhibited by substantially completely hydrolyzing the organotinR-oxysiloxane and replacing the alcohol from the hydrolysis reactionwith a water immiscible solvent such as xylene. It appears that somepolymerization occurs in the xylene, forming a solution of polymericmaterial, since the solution becomes viscous. The polymeric material inthe solution can be considered for two different ranges of tin tosilicon ratio. As pointed out above, when the ratio of tin atoms tosilicon atoms in a polymer is less than about 2:5, appreciablecross-linking can occur for forming solid films suitable as binders incoating compositions. When the ratio of tin atoms to silicon atoms in apolymer is more than about 2:5, steric hindrances inhibit cross-linkingand an essentially linear polymer is obtained.

When the tin to silicon ratio is more than about 2:5, it appears thatlinear polymerization of prepolymer occurs as alcohol is distilled fromthe solution, resulting in a solution of polymeric material in waterimmiscible solvent where the polymeric material may be similar to thepolymer obtained by evaporating the alcohol and forming a film, forexample. This appears so since the solution is somewhat similar to asolution made by redissolving in water immiscible solvent a film made byevaporating alcohol from a prepolymer solution. It is believed, however,that the polymeric material in a solution made by mixing waterimmiscible solvent with the water miscible solvent and then distillingoff the water miscible solvent has greater polymerization that aredissolved polymer. The elevated temperature used for distillation isbelieved to promote added polymerization of the polymeric material. Itis desirable to directly transfer from a water miscible solvent to awater immiscible solvent since appreciably faster and easier than goingthrough a solid state.

When the tin to silicon ratio is less than about 2:5, the prepolymer cancross-link when alcohol evaporates from a solution. Surprisingly,however, when a water immiscible solvent such as xylene is added and thealcohol distilled from the solution, cross-linking is inhibited and asolution containing organotin substituted siloxane polymeric materialresults. Some polymerization of the prepolymer is believed to occursince viscosity of a xylene solution is noticeably higher than viscosityof an original ethyl alcohol solution. The polymeric material in thexylene solution is not completely cross-linked, otherwise it would notbe retained in solution. Neither the exact state of the polymericmaterial nor the reasons for this effect are known. Such a solutioncannot be made by redissolving a solidified polymer since thecross-linked polymer is not soluble in xylene or similar waterimmiscible solvents.

Formation of a substantially completely hydrolyzed solution of polymericmaterial in a water immiscible solvent can be quite advantageous. Byreplacing water miscible solvent with water immiscible solvent, thepolymeric material can be made compatible with a variety of coatingingredients with which it is not compatible before hydrolysis and/or inthe presence of ethanol or other water miscible solvents. For example,hydrolyzed polymeric material in xylene is compatible with chlorinatedrubber coating compositions. Further, by this technique, entrapment ofresidual ethanol or other product of the hydrolysis reaction in thecoating film is prevented. Polymers with high tin content areparticularly susceptible to this condition.

Preparation of a solution containing hydrolyzed polymeric material canbe understood by reference to an exemplary embodiment. Thus, forexample, tributyltin ethoxysiloxane is dissolved in a water misciblesolvent such as ethanol. This precursor is hydrolyzed by adding ahydrolysis catalyst and water. Complete hydrolysis requires one mole ofwater per two moles of alkyl and/or alkoxyalkyl groups on the precursor.When the hydrolysis is acid catalyzed, a dilute aqueous solution of acidcan be slowly added to the solution of siloxane in ethyl alcohol withgood stirring. The addition can be at ambient or elevated temperature upto the temperature where decomposition of materials commences. When thereaction is catalyzed by hydroxyl ions, a source for generating hydroxylions such as an amine can be added to the ethyl alcohol solution ofsiloxane. Water is then slowly added to the well stirred mixture atambient or elevated temperature. Additional ethanol is a product of thehydrolysis.

A nonreactive or water immiscible solvent such as xylene is addedbefore, during, or after the hydrolysis. It can be desirable to add thewater immiscible solvent after hydrolysis in the case of acid catalysisand before hydrolysis in the case of hydroxyl catalysis.

When the hydrolysis is complete and the water immiscible solvent hasbeen added, temperature is raised sufficiently to remove ethanol bydistillation. The product is a solution of hydrolyzed polymeric materialwith a concentration dependent on the amount of water immiscible solventadded.

Although the example employs a specific siloxane and specific solvents,it will be apparent that a variety of materials as outlined above can beemployed. Preferably, the water miscible solvent is the same alcohol asresults from the hydrolysis reaction.

The water immiscible solvent is preferably xylene which is compatiblewith the ethyl alcohol of the preferred embodiment, as well as being agood solvent in coating compositions. Ethyl alcohol can be readilydistilled from such a mixture. Other suitable solvents can be selectedfrom the water immiscible solvents set forth in Table I of U.S. Pat. No.3,653,930, incorporated by reference hereinabove. Additional exemplarywater immiscible solvents include halogenated solvents such as methylenechloride, carbon tetrachloride, trichloroethylene andtrichlorotrifluoroethane; various alkanes such as pentane, hexane,octane or cyclohexane, or low melting waxes, some acetates such assec-butylacetate and tert-butylacetate; benzene; naphtha; toluene;methyl isobutyl ketone; mineral spirits; gasoline; turpentine, lograine,kerosene, and the like. The water immiscible solvent preferably has ahigher boiling point than the water miscible solvent or R-alcoholproduct of hydrolysis so that they can be removed by distillation. Othertechniques for removing the water miscible solvent, such as a molecularsieve, can also be employed in some embodiments.

Such a solution containing polymeric material can be mixed with avariety of ingredients for forming compositions for forming marineantifouling coatings. A broad variety of solvents, thixotropic agents,fillers, pigments, binders, and the like for marine antifouling coatingcompositions will be apparent. Oil based and water based paints, organicpolymer coating compositions such as acrylic, polyethylene,polypropylene, polystyrene, polyurethane, polyvinylchloride, chlorinatedrubber, alkyd resins, and similar coating materials can be included.Diluents, fillers, and pigments can be included in a coating compositionsuch as talc, limestone, diatomaceous earth, clay, iron oxides, zincoxides, lead oxide, titanium, dioxide, zinc dust, silica, wollastonite,barites, barium metaborate, chrome yellow, chrome green, copper, copperoxide, and the like. Organic dyes may also be used to color the product.

These and other features of the present invention will be furtherunderstood by reference to the following Examples.

EXAMPLE I

A precursor is formed by reacting 533.2 grams of Ethyl Silicate 40 with623.7 grams of tributyl tin acetate. Ethyl acetate from the reaction isremoved by distillation yielding 1000 grams of tributyltinethoxysiloxane or tributyltin ethyl silicate. This precursor is mixedwith 500 grams of ethyl alcohol, 20 grams of 2-ethylaminoethanol and 200grams of xylene. This solution is heated to about 50° C. and stirredvigorously while 61 grams of water is added dropwise to the solutionover a period of about 15 minutes. The temperature of the solution isthen increased to effect distillation of the ethyl alcohol. Distillationis complete when 942.5 grams of distillate is collected. The product,comprising a tributyltin substituted siloxane polymeric material inxylene, is a viscous liquid.

EXAMPLE II

A marine antifouling coating composition is formulated from a solutioncontaining polymeric material prepared in accordance with Example I andcontains the following ingredients: 98.0 grams of tributyltin silicate(from Example I), 77.0 grams of Alloprene X-10 (a chlorinated rubberbinder), 9.2 grams of coal tar, 36.3 grams of ww rosin, 5.6 grams ofpine oil, 15.8 grams of Shell solvent 1693 (a petroleum distillate), 3.0grams of Chevron solvent 265 (naphtha), 39.0 grams of xylene, 1.6 gramsof methanol, 56.0 grams of zinc oxide, 42.0 grams of red iron oxide,35.0 grams of talc, and 5.4 grams of Bentone 34 (dimethyldioctadecylammonium bentonite). When this composition is coated on a substrate andthe solvents evaporate, an adherent, tough, somewhat resilient marineantifouling coating results.

EXAMPLE III

A precursor is formed by reacting 745.2 grams of Ethyl Silicate 40 with453.3 grams of tributyltin acetate. Ethyl acetate from the reaction isremoved by distillation. A solution is formed comprising 200 grams ofthe resultant tributyltin ethyl silicate in 100 grams of ethanol. Thesolution is heated to 40° C. and stirred vigorously during slow dropwiseaddition of 17.8 grams of a 2% solution of sulfuric acid in watercombined with an equal volume of ethanol. When the addition of thismixture is complete, 50 milliliters of xylene is added to the solutionwhich is then heated to distill the ethyl alcohol. When about 150milliliters of distillate has been collected, an additional 200milliliters of xylene is added, distillation is considered complete whena total of 400 milliliters of distillate has been collected. The productis a clear liquid which becomes somewhat cloudy upon cooling. Fullcross-linking and precipitation of polymer was not observed. Thissolution containing polymeric material is useful in a variety of marineantifouling coating compositions.

What is claimed is:
 1. A method for preparing a solution containinghydrolyzed organotin siloxane polymeric material comprising the stepsof:combining an organotin R-oxy siloxane in which the ratio of tin atomsto silicon atoms is in the range of 1:50 to 1:1, where R represents agroup consisting of alkyl and alkoxyalkyl radicals containing less thansix carbon atoms, a water miscible solvent, water, a hydrolysiscatalyst, and a water immiscible solvent; and after hydrolysis of theorganotin R-oxy siloxane, removing by distillation the water misciblesolvent and R-alcohol from the hydrolysis reaction.
 2. A method asrecited in claim 1 wherein sufficient water is combined forsubstantially completely hydrolyzing the organotin R-oxy siloxane.
 3. Amethod as recited in claim 1 wherein the water miscible solventcomprises R-alcohol.
 4. A method as recited in claim 3 wherein R is theethyl radical.
 5. A method as recited in claim 4 wherein the waterimmiscible solvent comprises xylene.
 6. A method as recited in claim 1wherein the water immiscible solvent comprises xylene.
 7. A method asrecited in claim 6 wherein sufficient water is combined forsubstantially completely hydrolyzing the organotin R-oxy siloxane.
 8. Amethod as recited in claim 1 wherein the water immiscible solvent isadded after hydrolysis and before distillation.
 9. A method as recitedin claim 1 wherein the ratio of tin atoms to silicon atoms in theorganotin R-oxy siloxane is less than about 2:5.
 10. A method forpreparing a solution containing hydrolyzed organotin substitutedsiloxane polymeric material comprising the steps of:combining aprecursor having the formula: ##STR7## wherein m is from about 1 toabout 10, each X is independently selected from the group consisting ofR and Y, R is selected from the group consisting of alkyl andalkoxyalkyl radicals containing less than about six carbon atoms, andeach Y is independently a trisubstituted tin radical having the formula:##STR8## where R₁, R₂, and R₃ are independently selected from the groupconsisting of alkyl, cycloalkyl, and aryl radicals, and contain incombination up to about eighteen carbon atoms and wherein the ratio oftin atoms to silicon atoms in the precursor is in the range of fromabout 1:50 to 1:1; a water miscible solvent; water; a source of ionsselected from the group consisting of hydrogen ion and hydroxyl ion; anda water immiscible solvent having a boiling point higher than theboiling point of the water miscible solvent; and after hydrolysis of theprecursor removing by distillation the water miscible solvent andR-alcohol from the hydrolysis reaction.
 11. A method as recited in claim10 wherein m is an average of about five.
 12. A method as recited inclaim 10 wherein the water immiscible solvent is added after hydrolysisand before distillation.
 13. A method as recited in claim 10 wherein theratio of tin atoms to silicon atoms in the precursor is less than about2:5.
 14. A method as recited in claim 10 wherein R is ethyl.
 15. Amethod as recited in claim 14 wherein the water miscible solventcomprises ethyl alcohol.
 16. A method as recited in claim 15 wherein thewater immiscible solvent comprises xylene.
 17. A method as recited inclaim 10 wherein the water immiscible solvent comprises xylene.
 18. Amethod as recited in claim 10 wherein sufficient water is included forsubstantially completely hydrolyzing the precursor.
 19. A method forpreparing a solution containing hydrolyzed organotin siloxane polymericmaterial comprising the steps of:combining trisubstituted-organotinethoxysiloxane in which the ratio of tin atoms to silicon atoms in theorganotin ethoxysiloxane is in the range of from about 1:50 to 1:1, witha water miscible solvent, a source of hydroxyl ion, and a waterimmiscible solvent; gradually adding water for hydrolyzing the organotinethoxysiloxane; and removing by distillation the water miscible solventand ethyl alcohol from such hydrolysis.
 20. A method as recited in claim19 wherein sufficient water is added for substantially completelyhydrolyzing the organotin ethoxysiloxane.
 21. A method as recited inclaim 19 wherein the water miscible solvent comprises ethyl alcohol. 22.A method as recited in claim 21 wherein the water immiscible solventcomprises xylene.
 23. A method as recited in claim 19 wherein the ratioof tin atoms to silicon atoms in the organotin ethoxysiloxane is lessthan about 2:5.
 24. A method as recited in claim 19 wherein theorganotin radical comprises tributyltin.
 25. A method for preparing asolution containing hydrolyzed organotin siloxane polymeric materialcomprising the steps of:combining a trisubstituted-organotinethoxysiloxane in which the ratio of tin atoms to silicon atoms in theorganotin ethoxysiloxane is in the range of from about 1:50 to 1:1, anda water miscible solvent; gradually adding water and a source ofhydrogen ion for hydrolyzing the organotin ethoxysiloxane; adding awater immiscible solvent; and removing by distillation the watermiscible solvent and ethyl alcohol from such hydrolysis.
 26. A method asrecited in claim 25 wherein sufficient water is added for substantiallycompletely hydrolyzing the organotin ethoxysiloxane.
 27. A method asrecited in claim 25 wherein the water miscible solvent comprises xylene.28. A method as recited in claim 25 wherein the water immiscible solventcomprises xylene.
 29. A method as recited in claim 25 wherein the ratioof tin atoms to silicon atoms in the organotin ethoxysiloxane is lessthan about 2:5.
 30. A method as recited in claim 25 wherein theorganotin radical comprises tributyltin.
 31. A method for preparing asolution containing hydrolyzed organotin siloxane polymeric materialcomprising the steps of:reacting sufficient ethoxysiloxane and atrisubstituted tin compound selected from the group consisting oftributyltin acetate and bis-tributyltin oxide for forming a precursor inwhich the ratio of tin atoms to silicon atoms is in the range of fromabout 1:50 to 1:1; dissolving the precursor in ethyl alcohol; addingwater and a source of hydrolysis catalyst selected from the groupconsisting of hydrogen ion and hydroxyl ion to the precursor solutionfor forming a hydrolyzed prepolymer in solution in ethyl alcohol; addinga water immiscible solvent to the solution of prepolymer in ethylalcohol; and removing the ethyl alcohol by distillation.
 32. A method asrecited in claim 31 wherein the water immiscible solvent is compatiblewith a chlorinated rubber binder for a marine antifouling coating.
 33. Amethod as recited in claim 31 wherein the water immiscible solventcomprises xylene.
 34. A method as recited in claim 34 wherein the ratioof tin atoms to silicon atoms in the organotin ethoxysiloxane is lessthan about 2:5.
 35. A method as recited in claim 31 wherein the waterimmiscible solvent is added before the water.
 36. A solution comprisinga water immiscible solvent containing a polymeric material consistingessentially of substantially completely hydrolyzed organotin substitutedsiloxane dissolved in the solvent, where the ratio of tin atoms tosilicon atoms in the polymeric material is in the range of from about1:50 to 2:5.
 37. A solution as recited in claim 36 wherein the organotinmoiety comprises tributyltin radical.
 38. A solution as recited in claim36 wherein the water immiscible solvent comprises xylene.
 39. A solutioncomprising xylene containing a substantially completely hydrolyzedpolymeric tributyltin substituted siloxane dissolved in the xylene wherethe ratio of tin atoms to silicon atoms in the siloxane is in the rangeof from about 1:50 to 2:5.